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1、abaqus建模中映射节点的方法Mapping a set of nodes from one coordinate system to another You can map a set of nodes from one coordinate system to another. You can also rotate, translate, or scale the nodes in a set by using a more direct method instead of coordinate system mapping. These capabilities are useful
2、 for many geometric situations: a mesh can be generated quite easily in a local coordinate system (for example, on the surface of a cylinder) using other methods and then can be mapped into the global (X, Y, Z) system. In other cases some parts of your model need to be translated or rotated along a
3、given axis or scaled with respect to one point. The mapping capability cannot be used in a model defined in terms of an assembly of part instances. The following different mappings are provided: a simple scaling; a simple shift and/or rotation; skewed Cartesian; cylindrical; spherical; toroidal; and
4、, in Abaqus/Standard only, blended quadratic. The first five of these mappings are shown in Figure 2.1.113. Figure 2.1.113 Coordinate systems; angles are in degrees. Blended quadratic mapping is shown in Figure 2.1.114. Figure 2.1.114 Use of blended quadratic mapping to develop a solid mesh onto a c
5、urved block. In all cases the coordinates of the nodes in the set are assumed to be defined in the local system: these local coordinates at each node are replaced with the global Cartesian (X, Y, Z) coordinates defined by the mapping. All angular coordinates should be given in degrees. You can use e
6、ither coordinates or node numbers to define the new coordinate system, the axis of rotation and translation, or the reference point used for scaling. The mapping capability can be used several times in succession on the same nodes, if required. Scaling the local coordinates before they are mapped Fo
7、r all mappings except the blended quadratic mapping, you can specify a scaling factor to be applied to the local coordinates before they are mapped. This facility is useful for “stretching” some of the coordinates that are given. For example, in cases where the local system uses some angular coordin
8、ates and some distance coordinates (cylindrical, spherical, etc.), it may be preferable to generate the mesh in a system that uses distance measures in the angular directions and then scale onto the angular coordinate system for the mapping. Two different scaling methods are available. Specifying th
9、e scaling factors directly A first method of scaling the nodes with respect to the origin of the local system is to specify the scale factors directly. In this case the scaling is done at the same time as the mapping from one coordinate system to another. Input File Usage: *NMAP, NSET=name first dat
10、a line second data line scale factor for first local coord, scale factor for second local coord, scale factor for third local coord Specifying the scaling with respect to a reference point Alternatively, you can scale with respect to a point other than the origin. The reference point with respect to
11、 which the scaling is done can be defined by using either its coordinates or the user node number. Input File Usage: Use the following option to define the scaling reference point by using its coordinates (default): *NMAP, TYPE=SCALE, DEFINITION=COORDINATES X-coordinate of reference point, Y-coordin
12、ate of reference point, Z-coordinate of reference point scale factor for first local coord, scale factor for second local coord, scale factor for third local coord Use the following option to define the scaling reference point by using its node number: *NMAP, TYPE=SCALE, DEFINITION=NODES Local node
13、number of the reference point scale factor for first local coord, scale factor for second local coord, scale factor for third local coord Introducing a simple shift and/or rotation by mapping from one coordinate system to another In the case of a simple shift and/or rotation, point a in Figure 2.1.1
14、13 defines the origin of the local rectangular coordinate system defining the map. The local -axis is defined by the line joining points a and b. The local plane is defined by the plane passing through points a, b, and c. Input File Usage: *NMAP, NSET=name, TYPE=RECTANGULAR Introducing a pure shift
15、by specifying the axis and magnitude of the translation You can define a pure translation (or shift) to move a set of nodes by a prescribed value along a desired axis. You must specify the axis of translation by providing either the coordinates or the two node numbers defining this axis, and you mus
16、t prescribe the magnitude of the translation. Input File Usage: Use the following option to specify the axis of translation using coordinates (default): *NMAP, NSET=name, TYPE=TRANSLATION, DEFINITION=COORDINATES Use the following option to specify the axis of translation using node numbers: *NMAP, N
17、SET=name, TYPE=TRANSLATION, DEFINITION=NODES Introducing a pure rotation by specifying the axis, origin, and angle of the rotation You can define a rotation of a set of nodes by providing the axis of rotation, the origin of rotation, and the magnitude of the rotation. You must specify the axis of ro
18、tation by providing either the coordinates or the two node numbers defining this axis. You must specify the origin of the rotation by providing either the coordinates or the node number at the origin of rotation. Finally, you must specify the angle of the rotation in degrees. Input File Usage: Use t
19、he following option to specify the axis of rotation using coordinates (default): *NMAP, NSET=name, TYPE=ROTATION, DEFINITION=COORDINATES Use the following option to specify the axis of rotation using node numbers: *NMAP, NSET=name, TYPE=ROTATION, DEFINITION=NODES Mapping from cylindrical coordinates
20、 For mapping from cylindrical coordinates, point a in Figure 2.1.113 defines the origin of the local cylindrical coordinate system defining the map. The line going through point a and point b defines the -axis of the local cylindrical coordinate system. The local plane for is defined by the plane pa
21、ssing through points a, b, and c. Input File Usage: *NMAP, NSET=name, TYPE=CYLINDRICAL Mapping from skewed Cartesian coordinates For mapping from skewed Cartesian coordinates, point a in Figure 2.1.113 defines the origin of the local diamond coordinate system defining the map. The line going through
22、 point a and point b defines the -axis of the local coordinate system. The line going through point a and point c defines the -axis of the local coordinate system. The line going through point a and point d defines the -axis of the local coordinate system. Input File Usage: *NMAP, NSET=name, TYPE=DI
23、AMOND Mapping from spherical coordinates For mapping from spherical coordinates, point a in Figure 2.1.113 defines the origin of the local spherical coordinate system defining the map. The line going through point a and point b defines the polar axis of the local spherical coordinate system. The pla
24、ne passing through point a and perpendicular to the polar axis defines the plane. The plane passing through points a, b, and c defines the local plane. Input File Usage: *NMAP, NSET=name, TYPE=SPHERICAL Mapping from toroidal coordinates For mapping from toroidal coordinates, point a in Figure 2.1.11
25、3 defines the origin of the local toroidal coordinate system defining the map. The axis of the local toroidal system lies in the plane defined by points a, b, and c. The R-coordinate of the toroidal system is defined by the distance between points a and b. The line between points a and b defines the
26、 position. For every value of the -coordinate is defined in a plane perpendicular to the plane defined by the points a, b, and c and perpendicular to the axis of the toroidal system. lies in the plane defined by the points a, b, and c. Input File Usage: *NMAP, NSET=name, TYPE=TOROIDAL Mapping by mea
27、ns of blended quadratics To map by means of blended quadratics in Abaqus/Standard, you define the new (mapped) coordinates of up to 20 “control nodes”: these are the corner and midedge nodes of the block of nodes being mapped. The mapping in this case is like that of a 20-node brick isoparametric el
28、ement. Any of the midedge nodes can be omitted, thus allowing linear interpolation along that edge of the block. Abaqus/Standard does not check whether the nodes in the set lie within the physical space of the block defined by the corner and midedge nodes: these control nodes simply define mapping f
29、unctions that are then applied to all of the nodes in the set. The control nodes should define a “well”-shaped block; for example, midedge nodes should be close to the midpoint of the edge. Otherwise, the mapping can be very distorted. For example, the nodes of a crack-tip 20-node element with midside nodes at the quarter points will not map correctly and, therefore, should not be used as the control nodes. Blended mapping is only available for three-dimensional analyses. Input File Usage: *NMAP, NSET=name, TYPE=BLENDED
